Brief Report: Etanercept Inhibits the Tumor Necrosis Factor α-Driven Shift of Th17 Lymphocytes Toward a Nonclassic Th1 Phenotype in Juvenile Idiopathic Arthritis

Th17/1 and ex-Th17 cells are detected in patients with polyarticular juvenile arthritis and increase following treatment

BACKGROUND

A better understanding of the pathogenesis of polyarticular juvenile idiopathic arthritis (polyJIA) is needed to aide in the development of data-driven approaches to guide selection between therapeutic options. One inflammatory pathway of interest is JAK-STAT signaling. STAT3 is a transcription factor critical to the differentiation of inflammatory T helper 17 cells (Th17s). Previous studies have demonstrated increased STAT3 activation in adult patients with rheumatoid arthritis, but less is known about STAT3 activation in polyJIA. We hypothesized that Th17 cells and STAT3 activation would be increased in treatment-naïve polyJIA patients compared to pediatric controls.

METHODS

Blood from 17 patients with polyJIA was collected at initial diagnosis and again if remission was achieved (post-treatment). Pediatric healthy controls were also collected. Peripheral blood mononuclear cells were isolated and CD4 + T cell subsets and STAT activation (phosphorylation) were evaluated using flow cytometry. Data were analyzed using Mann-Whitney U and Wilcoxon matched-pairs signed rank tests.

RESULTS

Treatment-naïve polyJIA patients had increased Th17 cells (CD3 + CD4 + interleukin(IL)-17 +) compared to controls (0.15% v 0.44%, p < 0.05), but Tregs (CD3 + CD4 + CD25 + FOXP3 +) from patients did not differ from controls. Changes in STAT3 phosphorylation in CD4 + T cells following ex vivo stimulation were not significantly different in patients compared to controls. We identified dual IL-17 + and interferon (IFN)γ + expressing CD4 + T cells in patients, but not controls. Further, both Th17/1 s (CCR6 + CD161 + IFNγ + IL-17 +) and ex-Th17s (CCR6 + CD161 + IFNγ + IL-17neg) were increased in patients' post-treatment (Th17/1: 0.3% v 0.07%, p < 0.05 and ex-Th17s: 2.3% v 1.4%, p < 0.05). The patients with the highest IL-17 expressing cells post-treatment remained therapy-bound.

CONCLUSIONS

Patients with polyJIA have increased baseline Th17 cells, potentially reflecting higher tonic STAT3 activation in vivo. These quantifiable immune markers may identify patients that would benefit upfront from pathway-focused biologic therapies. Our data also suggest that inflammatory CD4 + T cell subsets not detected in controls but increased in post-treatment samples should be further evaluated as a tool to stratify patients in remission on medication. Future work will explore these proposed diagnostic and prognostic biomarkers.

From the Skin to Distant Sites: T Cells in Psoriatic Disease

Human skin has long been known as a protective organ, acting as a mechanical barrier towards the external environment. More recent is the acquisition that in addition to this fundamental role, the complex architecture of the skin hosts a variety of immune and non-immune cells playing preeminent roles in immunological processes aimed at blocking infections, tumor progression and migration, and elimination of xenobiotics. On the other hand, dysregulated or excessive immunological response into the skin leads to autoimmune reactions culminating in a variety of skin pathological manifestations. Among them is psoriasis, a multifactorial, immune-mediated disease with a strong genetic basis. Psoriasis affects 2-3% of the population; it is associated with cardiovascular comorbidities, and in up to 30% of the cases, with psoriatic arthritis. The pathogenesis of psoriasis is due to the complex interplay between the genetic background of the patient, environmental factors, and both innate and adaptive responses. Moreover, an autoimmune component and the comprehension of the mechanisms linking chronic skin inflammation with systemic and joint manifestations in psoriatic patients is still a major challenge. The understanding of these mechanisms may offer a valuable chance to find targetable molecules to treat the disease and prevent its progression to severe systemic conditions.

Th17 Cells: Orchestrators of Mucosal Inflammation and Potential Therapeutic Targets

T helper 17 (Th17) cells represent a specialized subgroup of effector CD4+ T cells known for their role in provoking neutrophil-driven tissue inflammation, particularly within mucosal tissues. Although they are pivotal for defending the host against extracellular bacteria and fungi, they have also been associated with development of various T cell-mediated inflammatory conditions, autoimmune diseases, and even cancer. Notably, Th17 cells exhibit a dual nature, with different Th17 cell subtypes showcasing distinct effector functions and varying capacities to incite autoimmune tissue inflammation. Furthermore, Th17 cells exhibit significant plasticity, which carries important functional implications, both in terms of their expression of cytokines typically associated with other effector T cell subsets and in their interactions with regulatory CD4+ T cells. The intricate balance of Th17 cytokines can also be a double-edged sword in inflammation, autoimmunity, and cancer. Within this article, we delve into the mechanisms that govern the differentiation, function, and adaptability of Th17 cells. We culminate with an exploration of therapeutic potentials in harnessing the power of Th17 cells and their cytokines. Targeted interventions to modulate Th17 responses are emerging as promising strategies for autoimmunity, inflammation, and cancer treatment. By precisely fine-tuning Th17-related pathways, we may unlock new avenues for personalized therapeutic approaches, aiming to restore immune balance, alleviate the challenges of these disorders, and ultimately enhance the quality of life for individuals affected by them.

A pathogenic integrated view explaining the different endotypes of asthma and allergic disorders

The inflammation of allergic diseases is characterized by a complex interaction between type 2 and type 3 immune responses, explaining clinical symptoms and histopathological patterns. Airborne stimuli activate the mucosal epithelium to release a number of molecules impacting the activity of resident immune and environmental cells. Signals from the mucosal barrier, regulatory cells, and the inflamed tissue are crucial conditions able to modify innate and adaptive effector cells providing the selective homing of eosinophils or neutrophils. The high plasticity of resident T- and innate lymphoid cells responding to external signals is the prerequisite to explain the multiplicity of endotypes of allergic diseases. This notion paved the way for the huge use of specific biologic drugs interfering with pathogenic mechanisms of inflammation. Based on the response of the epithelial barrier, the activity of resident regulatory cells, and functions of structural non-lymphoid environmental cells, this review proposes some immunopathogenic scenarios characterizing the principal endotypes which can be associated with a precise phenotype of asthma. Recent literature indicates that similar concepts can also be applied to the inflammation of other non-respiratory allergic disorders. The next challenges will consist in defining specific biomarker(s) of each endotype allowing for a quick diagnosis and the most effective personalized therapy.

Contribution of pathogenic T helper 1 and 17 cells to bursitis and tenosynovitis in polymyalgia rheumatica

Background

Although polymyalgia rheumatica (PMR) is a very common rheumatic inflammatory disease, current insight into the pathobiology of PMR is limited and largely based on studies in blood. We investigated T helper 1 (T_H1) and T helper 17 (T_H17) cell responses in blood, synovial fluid and bursa tissue of patients with PMR.

Materials and methods

Blood samples were collected from 18 patients with new-onset PMR and 32 healthy controls. Synovial fluid was aspirated from the inflamed shoulder bursae or biceps tendon sheath of 13 patients. Ultrasound-guided biopsies of the subacromial-subdeltoid (SASD) bursa were obtained from 11 patients. T cells were examined by flow cytometry, immunohistochemistry and immunofluorescence staining.

Results

Besides an increase of T_H17 (CD4⁺IL-17⁺IFN-γ^-) cells and T cytotoxic 17 (T_C17; CD8⁺IL-17⁺IFN-γ^-) cells, no other major changes were noted in the circulating T cell compartment of patients with PMR. Absolute numbers of CD4⁺ and CD8⁺ T cells were similar in blood and synovial fluid of patients with PMR. Synovial fluid T cells showed an effector-memory (CD45RO⁺CCR7^-) phenotype. Percentages of T_H1 (CD4⁺IFN-γ⁺IL-17^-) cells and T_H1/T_H17 (CD4⁺IFN-γ⁺IL-17⁺) cells, but not T_H17 or T_C17 cells, were increased in the synovial fluid. Bursa tissue biopsies contained a small number of T cells, which were mostly CD8 negative. The majority of bursa tissue T cells produced IFN-γ but not IL-17. For comparison, B cells were scarcely detected in the bursa tissue.

Conclusion

Although the circulating T_H17 cell pool is expanded in patients with PMR, our findings indicate that T_H1 cells are involved in the inflammation of bursae and tendon sheaths in this condition. Our study points towards the T_H1 cell pathway as a potential target for therapy in PMR.

Increased Development of Th1, Th17, and Th1.17 Cells Under T1 Polarizing Conditions in Juvenile Idiopathic Arthritis

In juvenile idiopathic arthritis (JIA) inflammatory T cells and their produced cytokines are drug targets and play a role in disease pathogenesis. Despite their clinical importance, the sources and types of inflammatory T cells involved remain unclear. T cells respond to polarizing factors to initiate types of immunity to fight infections, which include immunity types 1 (T1), 2 (T2), and 3 (T17). Polarizing factors drive CD4⁺ T cells towards T helper (Th) cell subtypes and CD8⁺ T cells towards cytotoxic T cell (Tc) subtypes. T1 and T17 polarization are associated with autoimmunity and production of the cytokines IFNγ and IL-17 respectively. We show that JIA and child healthy control (HC) peripheral blood mononuclear cells are remarkably similar, with the same frequencies of CD4⁺ and CD8⁺ naïve and memory T cell subsets, T cell proliferation, and CD4⁺ and CD8⁺ T cell subsets upon T1, T2, and T17 polarization. Yet, under T1 polarizing conditions JIA cells produced increased IFNγ and inappropriately produced IL-17. Under T17 polarizing conditions JIA T cells produced increased IL-17. Gene expression of IFNγ, IL-17, Tbet, and RORγT by quantitative PCR and RNA sequencing revealed activation of immune responses and inappropriate activation of IL-17 signaling pathways in JIA polarized T1 cells. The polarized JIA T1 cells were comprised of Th and Tc cells, with Th cells producing IFNγ (Th1), IL-17 (Th17), and both IFNγ-IL-17 (Th1.17) and Tc cells producing IFNγ (Tc1). The JIA polarized CD4⁺ T1 cells expressed both Tbet and RORγT, with higher expression of the transcription factors associated with higher frequency of IL-17 producing cells. T1 polarized naïve CD4⁺ cells from JIA also produced more IFNγ and more IL-17 than HC. We show that in JIA T1 polarization inappropriately generates Th1, Th17, and Th1.17 cells. Our data provides a tool for studying the development of heterogeneous inflammatory T cells in JIA under T1 polarizing conditions and for identifying pathogenic immune cells that are important as drug targets and diagnostic markers.

Treatment of male and female spontaneously hypertensive rats with TNF-α inhibitor etanercept increases markers of renal injury independent of an effect on blood pressure

Hypertension remains the leading risk factor for cardiovascular disease. Young females tend to be protected from hypertension compared with age-matched males. Although it has become increasingly clear that the immune system plays a key role in the development of hypertension in both sexes, few studies have examined how cytokines mediate hypertension in males versus females. We previously published that there are sex differences in the levels of the cytokine tumor necrosis factor (TNF)-α in spontaneously hypertensive rats (SHR). The goal of this study was to test the hypothesis that TNF-α inhibition with etanercept will lower BP in male and female SHR. However, as male SHR have a more pro-inflammatory status than female SHR, we further hypothesize that males will have a greater decrease in BP with TNF-α inhibition than females. Young adult male and female SHR were administered increasing doses of the TNF-α inhibitor etanercept or vehicle twice weekly for 31 days and BP was continuously measured via telemetry. Following treatment, kidneys and urine were collected and analyzed for markers of inflammation and injury. Despite significantly decreasing renal TNF-α levels, renal phospho-NFκB and urinary MCP-1 excretion, etanercept did not alter BP in either male or female SHR. Interestingly, treatment with etanercept increased urinary excretion of protein, creatinine and KIM-1 in both sexes. These results indicate that TNF-α does not contribute to sex differences in BP in SHR but may be vital in the maintenance of renal health.

Plasma interleukin-23 and circulating IL-17A+IFNγ+ ex-Th17 cells predict opposing outcomes of anti-TNF therapy in rheumatoid arthritis

OBJECTIVES

TNF-α inhibitors are widely used in rheumatoid arthritis (RA) with varying success. Response to TNF-α inhibition may reflect the evolution of rheumatoid inflammation through fluctuating stages of TNF-α dependence. Our aim was to assess plasma concentrations of Th-17-related cytokines and the presence of circulating effector T-cells to identify predictors of response to TNF-α inhibitors.

METHODS

Ninety-three people with RA were seen prior to and 4-6 months after commencing etanercept or adalimumab. Plasma concentrations of Th17-related cytokines, circulating effector T-cells, their production of relevant transcription factors and intracellular cytokines were measured at baseline. EULAR response criteria were used to define poor (ΔDAS28 ≤ 1.2 and/or DAS28 > 3.2) and good (ΔDAS28 > 1.2 and DAS28 ≤ 3.2) responders. Multivariate logistic regression was used to identify predictors of response.

RESULTS

Participants with plasma IL-23 present at baseline were more likely to be poor responders [15/20 (75%) of IL-23⁺ versus 36/73 (49.3%) of IL-23^-; p = 0.041]. While frequencies of Th1, Th17, ex-Th17 and T_reg cell populations were similar between good and poor responders to anti-TNF therapy, IL-17A⁺IFNγ⁺ ex-Th17 cells were more prevalent in good responders (0.83% of ex-T_H17 cells) compared to poor responders (0.24% of ex-Th17 cells), p = 0.023. Both plasma IL-23 cytokine status (OR = 0.17 (95% CI 0.04-0.73)) and IL-17A⁺IFNγ⁺ ex-Th17 cell frequency (OR = 1.64 (95% CI 1.06 to 2.54)) were independently associated with a good response to anti-TNF therapy. Receiver operator characteristic (ROC) analysis, including both parameters, demonstrated an area under the ROC curve (AUC) of 0.70 (95% CI 0.60-0.82; p = 0.001).

CONCLUSIONS

Plasma IL-23 and circulating IL-17A⁺IFNγ⁺ ex-Th17 cells are independently associated with response to anti-TNF therapy. In combination, plasma IL-23 and circulating IL-17A⁺IFNγ⁺ ex-Th17 cells provide additive value to the prediction of response to anti-TNF therapy in RA.

CD4+ T-Cell Plasticity in Non-Infectious Retinal Inflammatory Disease

Non-infectious uveitis (NIU) is a potentially sight-threatening disease. Effector CD4+ T cells, especially interferon-γ-(IFNγ) producing Th1 cells and interleukin-17-(IL-17) producing Th17 cells, are the major immunopathogenic cells, as demonstrated by adoptive transfer of disease in a model of experimental autoimmune uveitis (EAU). CD4+FoxP3+CD25+ regulatory T cells (Tregs) were known to suppress function of effector CD4+ T cells and contribute to resolution of disease. It has been recently reported that some CD4+ T-cell subsets demonstrate shared phenotypes with another CD4+ T-cell subset, offering the potential for dual function. For example, Th17/Th1 (co-expressing IFNγ and IL-17) cells and Th17/Treg (co-expressing IL-17 and FoxP3) cells have been identified in NIU and EAU. In this review, we have investigated the evidence as to whether these 'plastic CD4+ T cells' are functionally active in uveitis. We conclude that Th17/Th1 cells are generated locally, are resistant to the immunosuppressive effects of steroids, and contribute to early development of EAU. Th17/Treg cells produce IL-17, not IL-10, and act similar to Th17 cells. These cells were considered pathogenic in uveitis. Future studies are needed to better clarify their function, and in the future, these cell subsets may in need to be taken into consideration for designing treatment strategies for disease.

Clonally expanded PD-1hi CXCR5- CD4+ peripheral T helper cells promote differentiation of CD21lo/- CD11c+ double negative B cells in the joints of ANA+ JIA patients

OBJECTIVES

Antinuclear antibody (ANA) positive Juvenile Idiopathic Arthritis (JIA) is characterized by synovial B cell hyperactivity, but the precise role of CD4⁺ T cells in promoting local B cell activation is unknown. The objective of this study is to unravel the phenotype and function of synovial CD4⁺ T cells that promote the aberrant B cell activation in JIA.

METHODS

Flow cytometric analysis was performed to compare the phenotype and cytokine pattern of synovial fluid (SF) PD-1^hi CD4⁺ T cells with tonsil T_FH cells. TCRVB next generation sequencing was applied to analyze T cell subsets for signs of clonal expansion. The functional impact of these T cell subsets on B cells was dissected in in vitro co-cultures.

RESULTS

Multidimensional flow-cytometric analysis revealed the expansion of IL-21 and IFN-γ co-expressing PD-1^hi CXCR5^- HLA-DR⁺ CD4⁺ T cells that accumulate in the joints of ANA+ JIA patients. These T cells exhibited signs of clonal expansion with restricted TCR clonotypes. Phenotypically they resembled peripheral T helper (T_PH ) cells with an extrafollicular chemokine receptor pattern and high T-bet and Blimp-1 but low Bcl-6 expression. SF T_PH cells particularly skewed B cell differentiation towards a CD21^lo/- CD11c⁺ phenotype by provision of IL-21 and IFN-γ in vitro and correlated with the appearance of SF CD21^lo/- CD11c⁺ CD27^- IgM^- double-negative B cells (B_DN ) in situ.

CONCLUSION

Clonally expanded CD4⁺ T_PH cells accumulate in the joints of ANA+ JIA patients and particularly promote CD21^lo/- CD11c⁺ B_DN cell differentiation The expansion of T_PH and B_DN cells might reflect the autoimmune response present in the joints of ANA+ JIA patients.

Th17 Cells Contribute to the Pathology of Autoimmune Hypophysitis

Autoimmune hypophysitis is classified as primary if its origin is idiopathic and secondary if it develops as a consequence of treatment with immune checkpoint inhibitors. Expanding use of immunotherapy has been paralleled by the increasing hypophysitis prevalence. However, understanding of the immune responses driving the disease remains limited. Using a mouse model of primary hypophysitis, we have identified CD4⁺ T lymphocytes to be the main pituitary-infiltrating immune cell population. Functional analysis showed that they display a Th17 and Th1/Th17 phenotype. To examine involvement of proinflammatory Th1, Th17, and Th1/17 subsets in hypophysitis, we have isolated RNA from the formalin-fixed paraffin-embedded pituitary specimens from 16 hypophysitis patients (three of whom had hypophysitis secondary to immune checkpoint inhibitors), 10 patients with adenoma, and 23 normal pituitaries obtained at autopsy. Transcript levels of IFN-γ, IL-17A, IL-4, IL-10, TGF-β, CD4, CD8α, and class II MHC transactivator were analyzed by the reverse transcription-quantitative PCR (RT-qPCR). Pituitary glands of patients with hypophysitis showed significantly higher IL-17A, CD4, and class II MHC transactivator mRNA levels compared with adenoma and normal pituitaries. All three secondary hypophysitis patients showed detectable IL-17A levels, but other cytokines were not detected in their pituitaries. Levels of IFN-γ, IL-4, IL-10, and TGF-β did not differ between the groups. TGF-β transcript was found in significantly fewer hypophysitis pituitaries (2 out of 16) compared with adenoma (7 out of 10) and normal pituitaries (11 out of 23). Presence of TGF-β in two hypophysitis patients was associated with significantly lower IL-17A mRNA levels compared with hypophysitis patients with no detectable TGF-β (p = 0.03).

Human immunology and immunotherapy: main achievements and challenges

The immune system is a fascinating world of cells, soluble factors, interacting cells, and tissues, all of which are interconnected. The highly complex nature of the immune system makes it difficult to view it as a whole, but researchers are now trying to put all the pieces of the puzzle together to obtain a more complete picture. The development of new specialized equipment and immunological techniques, genetic approaches, animal models, and a long list of monoclonal antibodies, among many other factors, are improving our knowledge of this sophisticated system. The different types of cell subsets, soluble factors, membrane molecules, and cell functionalities are some aspects that we are starting to understand, together with their roles in health, aging, and illness. This knowledge is filling many of the gaps, and in some cases, it has led to changes in our previous assumptions; e.g., adaptive immune cells were previously thought to be unique memory cells until trained innate immunity was observed, and several innate immune cells with features similar to those of cytokine-secreting T cells have been discovered. Moreover, we have improved our knowledge not only regarding immune-mediated illnesses and how the immune system works and interacts with other systems and components (such as the microbiome) but also in terms of ways to manipulate this system through immunotherapy. The development of different types of immunotherapies, including vaccines (prophylactic and therapeutic), and the use of pathogens, monoclonal antibodies, recombinant proteins, cytokines, and cellular immunotherapies, are changing the way in which we approach many diseases, especially cancer.

Functionally distinct IFN-γ+ IL-17A+ Th cells in experimental autoimmune uveitis: T-cell heterogeneity, migration, and steroid response

Immunopathogenic roles for both Th1 (CD4⁺ IFN-γ⁺ ) and Th17 (CD4⁺ IL-17A⁺ ) cells have been demonstrated in experimental autoimmune uveitis (EAU). However, the role for Th17/Th1 (CD4⁺ T cells co-expressing IFN-γ and IL-17A) cells in EAU is not yet understood. Using interphotoreceptor retinoid-binding protein peptide-induced EAU in mice, we found increased levels of Th17/Th1 cells in EAU retinae (mean 9.6 ± 4.2%) and draining LNs (mean 8.4 ± 3.9%; p = 0.01) relative to controls. Topical dexamethasone treatment effectively reduced EAU severity and decreased retinal Th1 cells (p = 0.01), but had no impact on retinal Th17/Th1 or Th17 cells compared to saline controls. Using in vitro migration assays with mouse CNS endothelium, we demonstrated that Th17/Th1 cells were significantly increased within the migrated population relative to controls (mean 15.6 ± 9.5% vs. 1.9 ± 1.5%; p = 0.01). Chemokine receptor profiles of Th17/Th1 cells (CXCR3 and CCR6) did not change throughout the transendothelial migration process and were unaffected by dexamethasone treatment. These findings support a role for Th17/Th1 cells in EAU and their resistance to steroid inhibition suggests the importance of targeting both Th17 and Th17/Th1 cells for improving therapy.

Th17 lymphocyte-dependent degradation of joint cartilage by synovial fibroblasts in a humanized mouse model of arthritis and reversal by secukinumab

How T-helper (Th) lymphocyte subpopulations identified in synovial fluid from patients with juvenile idiopathic arthritis (JIA) (Th17, classic Th1, or nonclassic Th1) drive joint damage is of great interest for the possible use of biological drugs that inhibit the specific cytokines. Our objective was to clarify the role of such Th subpopulations in the pathogenesis of articular cartilage destruction by synovial fibroblasts (SFbs), and the effect of Th17 blockage in an animal model. SFbs were isolated from healthy subjects and patients with JIA, and peripheral blood Th lymphocytes subsets were obtained from healthy subjects. Fragments of human cartilage from healthy subjects in a collagen matrix containing JIA or normal SFbs grafted underskin in SCID mice were used to measure cartilage degradation under the effects of Th supernatants. JIA SFbs overexpress MMP9 and MMP2 and Th17 induce both MMPs in normal SFbs, while nonclassic Th1 upregulate urokinase plasminogen activator (uPA) activity. In vitro invasive phenotype of normal SFbs is stimulated with conditioned medium of Th17 and nonclassic-Th1. In the in vivo "inverse wrap" model, normal SFbs stimulated with supernatants of Th17-lymphocytes and nonclassic Th1 produced a cartilage invasion and degradation similar to JIA SFbs. Secukinumab inhibits the cartilage damage triggered by factors produced by Th17.

Early Prediction of Clinical Response to Etanercept Treatment in Juvenile Idiopathic Arthritis Using Machine Learning

Background and Aims

At present, there is a lack of simple and reliable model for early prediction of the efficacy of etanercept in the treatment of juvenile idiopathic arthritis (JIA). This study aimed to generate and validate prediction models of etanercept efficacy in patients with JIA before administration using machine learning algorithms based on electronic medical record (EMR).

Materials and Methods

EMR data of 87 JIA patients treated with etanercept between January 2011 and December 2018 were collected retrospectively. The response of etanercept was evaluated by using DAS44/ESR-3 simplified standard. The stepwise forward and backward method based on information gain was applied to select features. Five machine learning algorithms, including Extreme Gradient Boosting (XGBoost), Random Forest (RF), Gradient Boosting Decision Tree (GBDT), Extremely Random Trees (ET) and Logistic Regression (LR) were used for model generation and validation with fifty-fold stratified cross-validation. EMR data of additional 14 patients were collected for external validation of the model.

Results

Tender joint count (TJC), Time interval, Lymphocyte percentage (LYM), and Weight were screened out and included in the final model. The model generated by the XGBoost algorithm based on the above 4 features had the best predictive performance: sensitivity 75%, specificity 66.67%, accuracy 72.22%, AUC 79.17%, respectively.

Conclusion

A pre-administration model with good prediction performance for etanercept response in JIA was developed using advanced machine learning algorithms. Clinicians and pharmacists can use this simple and accurate model to predict etanercept response of JIA early and avoid treatment failure or adverse effects.

Association of Pathogenic Th17 Cells with the Disease Severity and Its Potential Implication for Biological Treatment Selection in Psoriasis Patients

Psoriasis is an inflammatory autoimmune disease characterized by cutaneous lesions in plaques. It has been proposed that the immune response has a key role in the disease progression. Particularly, the Th17 cells through IL-17 can contribute to maintain the inflammatory process. The pathogenic Th17 phenotype has been described in human diseases and associated with high severity in inflammatory experimental models. However, it is not clear if the pathogenic phenotype could be present in the skin and peripheral blood as well as its possible association to severity in psoriasis. In the lesional skin, we found high infiltration of Th17 cells and the pathogenic phenotype, finding a correlation between the frequency of Th17 cells and the Psoriasis Area and Severity Index (PASI) score. In peripheral blood, we observed a pool of Th17 lymphocytes with potential to acquire pathogenic features. Interestingly, the percentage of pathogenic Th17 cells (CD4⁺ RORγt⁺ IFN-γ⁺) correlates with disease severity. Moreover, we distinguished three groups of patients based on their IL-17/IFN-γ production by Th17 lymphocytes, which seems to be related with a dynamic or stable potential to express these cytokines. Remarkably, we evaluated the cytokine production by Th17 cells as an immunological marker for the adequate selection of biologic therapy. We found that patients analyzed by this immunological approach and treated with antibodies against IL-17 and TNFα showed great improvement depicted by reduction in PASI and Dermatology Life Quality Index (DLQI) score as well as the percentage of Body Surface Area (BSA). Altogether, our results highlight the importance of the assessment of the pathogenic phenotype in Th17 cells as an immune personalized analysis with the potential to support the therapy choice in the clinical practice.

Brown adipose tissue ameliorates autoimmune arthritis via inhibition of Th17 cells

The functions of adipose tissue are associated with autoimmune diseases, such as rheumatoid arthritis (RA). Some studies have shown that the three compositions of adipose tissue (white, brown, and beige) have different functions. Brown adipose tissue (BAT) is known to secrete several factors that differ from those in white adipose tissue. This suggests that BAT might have potential positive advantages in the physiology of autoimmune diseases. We compared the functions of collagen-induced arthritis mice-derived BAT (CIA BAT) with normal mice-derived BAT. DBA/1J mice (6-7 weeks of age) were immunized by intradermal injection at the base of the tail with 100 μg of bovine type II collagen (CII) emulsified in complete Freund's adjuvant. Immunized mice then received booster immunizations by intraperitoneal injection with 100 μg of CII in incomplete Freund's adjuvant. We transplanted CIA BAT and normal BAT into CIA recipient mice. After transplantation, we measured the functions of CIA BAT and normal BAT in mice. Normal BAT-transplanted mice showed significantly lower scores of bone damage, inflammation, and cartilage damage. The proinflammatory cytokines in normal BAT-transplanted mice, such as IL-12, IL-17, IL-6, and tumor necrosis factor-α (TNF-α), tended to decrease. Microarray analysis showed that the PI3K-AKT signaling pathway and IL-17 levels of CIA BAT tissues were significantly higher than those of normal BAT tissues. These results suggest that the transplantation of normal brown fat may have a therapeutic effect in RA patients.

T-bet Expression in Peripheral Th17.0 Cells Is Associated With Pulmonary Function Changes in Sarcoidosis

Background: Interferon-gamma (IFN-γ) is a key mediator of sarcoidosis-related granulomatous inflammation. Previous findings of IFN-γ-producing Th17 cells in bronchoalveolar lavage fluid from sarcoidosis patients invokes the transition of Th17.0 cells to Th17.1 cells in the disease's pathogenesis. Since the T-bet transcription factor is crucial for this transition, the goal of this study was to determine if T-bet expression in Th17.0 cells reflects the extent of granulomatous inflammation in sarcoidosis patients as assessed by clinical outcomes.

Methods: Using a case-control study design, we identified two groups of sarcoidosis subjects (total N = 43) with pulmonary function tests (PFTs) that either (1) changed (increased or decreased) longitudinally or (2) were stable. We used flow cytometry to measure the transcription factors T-bet and RORγt in Th1, Th17.0, and Th17.1 cell subsets defined by CCR6, CCR4 and CXCR3 in blood samples. We compared the percentages of T-bet⁺ cells in RORγt⁺Th17.0 cells (defined as CCR6⁺CCR4⁺CXCR3⁻) based on subjects' PFT group. We also assessed the relationship between the direction of change in PFTs with the changes in %T-bet⁺ frequencies using mixed effects modeling.

Results: We found that T-bet expression in subjects' RORγt⁺Th17.0 cells varied based on clinical outcome. The T-bet⁺ percentage of RORγt⁺Th17.0 cells was higher in the cases (subject group with PFT changes) as compared to controls (stable group) (27 vs. 16%, p = 0.0040). In comparisons before and after subjects' PFT changes, the T-bet⁺ frequency of RORγt⁺Th17.0 cells increased or decreased in the opposite direction of the PFT change. The percentage of these T-bet⁺ cells was also higher in those with greater numbers of involved organs. Serum levels of interferon-γ-induced chemokines, CXCL9, CXCL10, and CXCL11, and whole blood gene expression of IFN-γ-related genes including GBP1, TAP1, and JAK2 were independently positively associated with the T-bet⁺ frequencies of RORγt⁺Th17.0 cells.

Conclusions: These data suggest that expression of T-bet in Th17.0 cells could reflect the extent of granulomatous inflammation in sarcoidosis patients because they represent a transition state leading to the Th17.1 cell phenotype. These findings indicate that Th17 plasticity may be part of the disease paradigm.

T Helper Cells: The Modulators of Inflammation in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic neurodegenerative disease characterized by the progressive loss of axonal myelin in several areas of the central nervous system (CNS) that is responsible for clinical symptoms such as muscle spasms, optic neuritis, and paralysis. The progress made in more than one decade of research in animal models of MS for clarifying the pathophysiology of MS disease validated the concept that MS is an autoimmune inflammatory disorder caused by the recruitment in the CNS of self-reactive lymphocytes, mainly CD4⁺ T cells. Indeed, high levels of T helper (Th) cells and related cytokines and chemokines have been found in CNS lesions and in cerebrospinal fluid (CSF) of MS patients, thus contributing to the breakdown of the blood-brain barrier (BBB), the activation of resident astrocytes and microglia, and finally the outcome of neuroinflammation. To date, several types of Th cells have been discovered and designated according to the secreted lineage-defining cytokines. Interestingly, Th1, Th17, Th1-like Th17, Th9, and Th22 have been associated with MS. In this review, we discuss the role and interplay of different Th cell subpopulations and their lineage-defining cytokines in modulating the inflammatory responses in MS and the approved as well as the novel therapeutic approaches targeting T lymphocytes in the treatment of the disease.

Biological and clinical significance of T helper 17 cell plasticity

Mature T helper (Th) effector cells originate following antigen recognition by naive T precursors. The maturation process is accompanied by the acquisition of specific effector functions that distinguish at least three different T helper subsets: Th1, Th2 and Th17. In general, maturation of somatic cells is accompanied by terminal differentiation. However, accumulating evidence shows that effector T cells retain a certain degree of plasticity. This is especially true for Th17 cells, which have been shown to converge towards other phenotypes in response to specific microenvironmental pressure. In this review we will discuss the experimental evidence that supports the hypothesis of Th17 plasticity, with particular emphasis on the generation of Th17-derived 'non-classic' Th1 cells, and the molecular networks that control it. Moreover, we will consider why Th17 plasticity is important for host protection, but also why it can have pathogenic functions during chronic inflammation. Regarding the last point, we will discuss a possible role for biological drugs in the control of Th17 plasticity and disease course.

T-Cell Compartmentalization and Functional Adaptation in Autoimmune Inflammation: Lessons From Pediatric Rheumatic Diseases

Chronic inflammatory diseases are characterized by a disturbed immune balance leading to recurring episodes of inflammation in specific target tissues, such as the joints in juvenile idiopathic arthritis. The tissue becomes infiltrated by multiple types of immune cell, including high numbers of CD4 and CD8 T-cells, which are mostly effector memory cells. Locally, these T-cells display an environment-adapted phenotype, induced by inflammation- and tissue-specific instructions. Some of the infiltrated T-cells may become tissue resident and play a role in relapses of inflammation. Adaptation to the environment may lead to functional (re)programming of cells and altered cellular interactions and responses. For example, specifically at the site of inflammation both CD4 and CD8 T-cells can become resistant to regulatory T-cell-mediated regulation. In addition, CD8 and CD4 T-cells show a unique profile with pro- and anti-inflammatory features coexisting in the same compartment. Also regulatory T-cells are neither homogeneous nor static in nature and show features of functional differentiation, and plasticity in inflammatory environments. Here we will discuss the recent insights in T-cell functional specialization, regulation, and clonal expansion in local (tissue) inflammation.

Th17 and Th1 Lymphocytes in Oligoarticular Juvenile Idiopathic Arthritis

In the last years much attention has focused on the Th17 and Th1 phenotypes and on their pathogenic role in juvenile idiopathic arthritis, investigating how the cytokines produced by T helper cells act on resident cells on the synovia and which signal transduction pathways regulate Th17 cells proliferation and plasticity. In this context, an important milestone was represented by the identification of the non-classic Th1 phenotype, developed from the shift of Th17 cells. The cytokine TNF-α, beyond its well-known proinflammatory activity is involved in this process and this is one of the reasons why the TNF-α inhibitors are widely used in the treatment of juvenile idiopathic arthritis patients.

Impact of Aging on the Frequency, Phenotype, and Function of CD161-Expressing T Cells

Immune-aging is associated with perturbed immune responses in the elderly. CD161-expressing T cells, i.e., the previously described subsets of CD161⁺ CD4⁺ T cells, CD161^high CD8⁺ T cells, and CD161^int CD8⁺ T cells, are highly functional, pro-inflammatory T cells. These CD161-expressing T cells are critical in immunity against microbes, while possibly contributing to autoimmune diseases. So far, little is known about the impact of aging on the frequency, phenotype, and function of these CD161-expressing T cells. In the current study, we investigated the impact of aging on CD161⁺ CD4⁺ T cells, CD161^high CD8⁺ T cells, and CD161^int CD8⁺ T cells in peripheral blood samples of 96 healthy subjects (age 20–84). Frequencies of CD161⁺ CD4⁺ T cells and CD161^int CD8⁺ T cells were stable with aging, whereas frequencies of CD161^high CD8⁺ T cells declined. Although CD161^high CD8⁺ T cells were mostly T cell receptor-Vα7.2⁺ mucosal-associated invariant T cells, CD161 expressing CD4⁺ and CD8⁺ T cells showed a limited expression of markers for gamma–delta T cells or invariant natural killer (NK) T cells, in both young and old subjects. In essence, CD161-expressing T cells showed a similar memory phenotype in young and old subjects. The expression of the inhibitory NK receptor KLRG1 was decreased on CD161⁺ CD4⁺ T cells of old subjects, whereas the expression of other NK receptors by CD161-expressing T cells was unaltered with age. The expression of cytotoxic effector molecules was similar in CD161^high and CD161^int CD8⁺ T cells of young and old subjects. The ability to produce pro-inflammatory cytokines was preserved in CD161^high and CD161^int CD8⁺ T cells of old subjects. However, the percentages of IFN-γ⁺ and interleukin-17⁺ cells were significantly lower in CD161⁺ CD4⁺ T cells of old individuals than those of young individuals. In addition, aging was associated with a decrease of nonclassic T helper 1 cells, as indicated by decreased percentages of CD161-expressing cells within the IFN-γ⁺ CD4⁺ T cell compartment of old subjects. Taken together, aging is associated with a numerical decline of circulating CD161^high CD8⁺ T cells, as well as a decreased production of pro-inflammatory cytokines by CD161⁺ CD4⁺ T cells. These aging-associated changes could contribute to perturbed immunity in the elderly.

TNF-α-induced protein 3 (TNFAIP3)/A20 acts as a master switch in TNF-α blockade-driven IL-17A expression

BACKGROUND

Anti-TNF inhibitors successfully improve the quality of life of patients with inflammatory disease. Unfortunately, not all patients respond to anti-TNF therapy, and some patients show paradoxical immune side effects, which are poorly understood. Surprisingly, anti-TNF agents were shown to promote IL-17A production with as yet unknown clinical implications.

OBJECTIVE

We sought to investigate the molecular mechanism underlying anti-TNF-driven IL-17A expression and the clinical implications of this phenomenon.

METHODS

Fluorescence-activated cell sorting, RNA sequencing, quantitative real-time PCR, Western blotting, small interfering RNA interference, and kinase inhibitors were used to study the molecular mechanisms in isolated human CD4⁺ T cells from healthy donors. The clinical implication was studied in blood samples of patients with inflammatory bowel disease (IBD) receiving anti-TNF therapy.

RESULTS

Here we show that anti-TNF treatment results in inhibition of the anti-inflammatory molecule TNF-α-induced protein 3 (TNFAIP3)/A20 in memory CD4⁺ T cells. We found an inverse relationship between TNFAIP3/A20 expression levels and IL-17A production. Inhibition of TNFAIP3/A20 promotes kinase activity of p38 mitogen-activated protein kinase and protein kinase C, which drives IL-17A expression. Regulation of TNFAIP3/A20 expression and cognate IL-17A production in T cells are specifically mediated through TNF receptor 2 signaling. Ex vivo, in patients with IBD treated with anti-TNF, we found further evidence for an inverse relationship between TNFAIP3/A20 expression levels and IL-17A-producing T cells.

CONCLUSION

Anti-TNF treatment interferes in the TNFAIP3/A20-mediated anti-inflammatory feedback loop in CD4⁺ T cells and promotes kinase activity. This puts TNFAIP3/A20, combined with IL-17A expression, on the map as a potential tool for predicting therapy responsiveness or side effects of anti-TNF therapy. Moreover, it provides novel targets related to TNFAIP3/A20 activity for superior therapeutic regimens in patients with IBD.

Heterogeneity of Human CD4(+) T Cells Against Microbes

CD4(+) T helper (Th) cells play a central role in the adaptive immune response by providing help to B cells and cytotoxic T cells and by releasing different types of cytokines in tissues to mediate protection against a wide range of pathogenic microorganisms. These functions are performed by different types of Th cells endowed with distinct migratory capacities and effector functions. Here we discuss how studies of the human T cell response to microbes have advanced our understanding of Th cell functional heterogeneity, in particular with the discovery of a distinct Th1 subset involved in the response to Mycobacteria and the characterization of two types of Th17 cells specific for extracellular bacteria or fungi. We also review new approaches to dissect at the clonal level the human CD4(+) T cell response induced by pathogens or vaccines that have revealed an unexpected degree of intraclonal diversification and propose a progressive and selective model of CD4(+) T cell differentiation.

The Th17 Lineage: From Barrier Surfaces Homeostasis to Autoimmunity, Cancer, and HIV-1 Pathogenesis

The T helper 17 (Th17) cells represent a subset of CD4+ T-cells with unique effector functions, developmental plasticity, and stem-cell features. Th17 cells bridge innate and adaptive immunity against fungal and bacterial infections at skin and mucosal barrier surfaces. Although Th17 cells have been extensively studied in the context of autoimmunity, their role in various other pathologies is underexplored and remains an area of open investigation. This review summarizes the history of Th17 cell discovery and the current knowledge relative to the beneficial role of Th17 cells in maintaining mucosal immunity homeostasis. We further discuss the concept of Th17 pathogenicity in the context of autoimmunity, cancer, and HIV infection, and we review the most recent discoveries on molecular mechanisms regulating HIV replication/persistence in pathogenic Th17 cells. Finally, we stress the need for novel fundamental research discovery-based Th17-specific therapeutic interventions to treat pathogenic conditions associated with Th17 abnormalities, including HIV infection.

CCR6+ Th cells in the cerebrospinal fluid of persons with multiple sclerosis are dominated by pathogenic non-classic Th1 cells and GM-CSF-only-secreting Th cells

Considerable attention has been given to CCR6⁺ IL-17-secreting CD4⁺ T cells (Th17) in the pathology of a number of autoimmune diseases including multiple sclerosis (MS). However, other Th subsets also play important pathogenic roles, including those that secrete IFNγ and GM-CSF. CCR6 expression by Th17 cells allows their migration across the choroid plexus into the cerebrospinal fluid (CSF), where they are involved in the early phase of experimental autoimmune encephalomyelitis (EAE), and in MS these cells are elevated in the CSF during relapses and contain high frequencies of autoreactive cells. However, the relatively low frequency of Th17 cells suggests they cannot by themselves account for the high percentage of CCR6⁺ cells in MS CSF. Here we identify the dominant CCR6⁺ T cell subsets in both the blood and CSF as non-classic Th1 cells, including many that secrete GM-CSF, a key encephalitogenic cytokine. In addition, we show that Th cells secreting GM-CSF but not IFNγ or IL-17, a subset termed GM-CSF-only-secreting Th cells, also accumulate in the CSF. Importantly, in MS the proportion of IFNγ- and GM-CSF-secreting T cells expressing CCR6 was significantly enriched in the CSF, and was elevated in MS, suggesting these cells play a pathogenic role in this disease.

The Plasticity of Th17 Cells in the Pathogenesis of Rheumatoid Arthritis

Helper T (Th) cells play an important role in the pathogenesis of autoimmune diseases, including rheumatoid arthritis (RA). It has been revealed that Th17 cells can shift to Th1 cells (i.e., “nonclassic Th1 cells”), which are reported to be more pathogenic than Th17 cells per se. Thus, the association of Th cells in the pathogenesis of autoimmune disease has become more complicated. We recently reported using peripheral blood from untreated and early-onset RA patients that the ratio of CD161+Th1 cells (i.e., Th17-derived Th1 cells to CD161+Th17 cells) is elevated and that levels of interferon-γ (IFNγ)+Th17 cells are inversely correlated with levels of anti-CCP antibodies. Here, we review the plasticity of Th17 cells in the pathogenesis of RA, suggesting possible implications for novel therapies.

Musculin inhibits human T-helper 17 cell response to interleukin 2 by controlling STAT5B activity

We recently demonstrated that human T-helper (Th) 17 cells, unlike Th1 cells, do not proliferate in response to T-cell receptor stimulation, mainly because of their reduced capacity to produce and respond to IL-2. In this study, we show that their lower responsiveness to IL-2 is due to the selective expression of Musculin (MSC), a member of the basic helix-loop-helix transcription factors. We show that MSC expression in human Th17 cells is retinoic acid orphan receptor (ROR)γt-dependent, and allows the upregulation of PPP2R2B, a regulatory member of the protein phosphatase 2A (PP2A) enzyme. High PPP2R2B levels in human Th17 cells were responsible for the reduced STAT5B Ser-193 phosphorylation upon IL-2 signalling and, therefore, impaired STAT5B DNA binding and transcriptional activity on IL-2 target genes. PP2A, observed in Th17 cells, controls also STAT3, dephosphorylating Ser727, thus increasing its activity that plays a crucial role in Th17 development and/or maintenance. Thus, our findings identify an additional mechanism responsible for the limited expansion of human Th17 cells, and could provide a further explanation for the rarity of these cells in inflamed tissues.

Detection of IFN-γ+IL-17+ cells in salivary glands of patients with Sjögren's syndrome and Mikulicz's disease: Potential role of Th17•Th1 in the pathogenesis of autoimmune diseases

  Objective: Th17 cells, which mainly produce interleukin (IL)-17, have been suggested to play a critical role in the pathogenesis of autoimmune diseases. The plasticity of Th17 cells, in which these cells shift to a Th1 phenotype in the presence of IL-12, has recently been reported. However, the role of IL-17 in Sjögren's syndrome (SS) and Mikulicz's disease (MD) currently remains unknown.

PATIENTS AND METHODS

The submandibular salivary gland and lymph node of a MD patient and the salivary glands of 15 SS patients were collected. IFN-γ+ cells, IL-17+ cells, and IFN-γ+IL-17+ cells were detected by immunohistochemical staining.

RESULTS

IFN-γ+ cells, IL-17+ cells, and IFN-γ+IL-17+ cells were detected in the submandibular salivary gland and lymph node of the MD patient and salivary glands of the 15 SS patients.

DISCUSSION

IFN-γ+IL-17+cells in the salivary glands of patients were speculated to be Th1/Th17 cells in the present study. Th1/Th17 cells are known to be derived from Th17 cells and differentiate into Th1 cells, and IL-17-derived Th1 cells have been suggested to induce the deterioration of juvenile idiopathic arthritis (JIA). Thus, Th1/Th17 cells may play an important role in the pathogenesis of SS and MD.

CONCLUSION

IFN-γ+, IFN-γ+IL-17+, and IL-17+ cells were detected in the submandibular salivary gland and lymph node of a MD patient and the salivary glands of 15 SS patients.

Chitinase 3-like-1 is produced by human Th17 cells and correlates with the level of inflammation in juvenile idiopathic arthritis patients

BACKGROUND

CHI3L1 is a chitinase-like protein without enzymatic activity, produced by activated macrophages, chondrocytes, neutrophils. Recent studies on arthritis, asthma, and inflammatory bowel diseases suggest that chitinases are important in inflammatory processes and tissue remodeling, but their production by human T cells, has never been reported.

METHODS

A microarray analysis of gene expression profile was performed on Th17 and classic Th1 cell clones and CHI3L1 was found among the up-regulated genes on Th17 cells. Different types of helper T cell clones (TCCs) were then evaluated by Real Time PCR (RT-PCR) for CHI3L1 mRNA expression; protein expression was investigated in cell lysates by western blotting and in cultures supernatants by ELISA. ELISA was also used to measure CHI3L1 in the serum and in the synovial fluid (SF) of juvenile idiopathic arthritis (JIA) patients.

RESULTS

At mRNA level CHI3L1 was highly expressed by Th17, Th17/Th1, non classic Th1 and even in Th17/Th2 cell clones, whereas it was virtually absent in CD161- classic Th1 and Th2 TCCs. CHI3L1 was also detected in cell culture supernatants of Th17 and Th17-derived cells but not of classic Th1. Moreover CHI3L1 was higher in the SF than in serum of JIA patients, and it positively correlated with the frequency of Th17 and non-classic Th1 cells in SF. CHI3L1 in SF also positively correlated with the C reactive protein (CRP) serum levels, and with the levels of some proinflammatory cytokines, such as IL-6 and p40, which is the common subunit of IL12 and IL23.

CONCLUSIONS

Here we describe for the first time CHI3L1 production by T cells owing the Th17 family. Moreover the positive correlation found between the frequency of Th17 and Th17-derived cell subsets and CHI3L1 levels in SF of JIA patients, in agreement with the suggested role of these cells in inflammatory process, candidates CHI3L1 as a possible biological target in JIA treatment.

T cell subpopulations in juvenile idiopathic arthritis and their modifications after biotherapies

Inflammatory T cells are thought to be central to the pathogenesis of juvenile idiopathic arthritis. In particular, recent evidence has underlined the importance of a balance between Th17 and Treg cells. Several mechanisms have come to light that control this reciprocal relationship. Moreover, it has been shown that in certain conditions, Th17 cells can shift toward a nonclassic Th1 phenotype. Anti-rheumatic biologic therapies may interfere with these mechanisms and re-establish immune tolerance.

Immune pathogenesis of psoriasis

The article presents current information about the immune mechanisms of psoriasis. Inflammation in the skin of psoriasis patients is considered as an autoimmune process, in which a key role is played by T-cells sensitized to keratinocytes. One of the most probable self-antigens that trigger an immune inflammation in psoriasis may be cytosolic DNA. We describe the functions of the subpopulations of immune cells and the effects of secreted cytokines in the pathogenesis of psoriasis: the dendritic cells - langerhans cells, plasmacytoid dendritic cells, CD11c+ dendritic cells ; T-cells - T helper type 1 and 17, cytotoxic t lymphocytes, T-regulatory lymphocytes. Important role in the development of relapses of psoriasis is plays a formation in the skin of patients with T-cell memory and intradermal proliferation of T-cells.

Th1-Induced CD106 Expression Mediates Leukocytes Adhesion on Synovial Fibroblasts from Juvenile Idiopathic Arthritis Patients

This study tested the hypothesis that subsets of human T helper cells can orchestrate leukocyte adhesion to synovial fibroblasts (SFbs), thus regulating the retention of leukocytes in the joints of juvenile idiopathic arthritis (JIA) patients. Several cell types, such as monocytes/macrophages, granulocytes, T and B lymphocytes, SFbs and osteoclasts participate in joint tissue damage JIA. Among T cells, an enrichment of classic and non-classic Th1 subsets, has been found in JIA synovial fluid (SF), compared to peripheral blood (PB). Moreover, it has been shown that IL-12 in the SF of inflamed joints mediates the shift of Th17 lymphocytes towards the non-classic Th1 subset. Culture supernatants of Th17, classic and non-classic Th1 clones, have been tested for their ability to stimulate proliferation, and to induce expression of adhesion molecules on SFbs, obtained from healthy donors. Culture supernatants of both classic and non-classic Th1, but not of Th17, clones, were able to induce CD106 (VCAM-1) up-regulation on SFbs. This effect, mediated by tumor necrosis factor (TNF)-α, was crucial for the adhesion of circulating leukocytes on SFbs. Finally, we found that SFbs derived from SF of JIA patients expressed higher levels of CD106 than those from healthy donors, resembling the phenotype of SFbs activated in vitro with Th1-clones supernatants. On the basis of these findings, we conclude that classic and non-classic Th1 cells induce CD106 expression on SFbs through TNF-α, an effect that could play a role in leukocytes retention in inflamed joints.

TGF-β converts Th1 cells into Th17 cells through stimulation of Runx1 expression

Differentiated CD4(+) T cells preserve plasticity under various conditions. However, the stability of Th1 cells is unclear, as is whether Th1 cells can convert into Th17 cells and thereby contribute to the generation of IFN-γ(+) IL-17(+) CD4(+) T cells, the number of which correlates with severity of colitis. We investigated whether IFN-γ(+) Th1 cells can convert into Th17 cells under intestinal inflammation and the mechanisms involved. IFN-γ(Thy1.1+) Th1 cells were generated by culturing naïve CD4(+) T cells from IFN-γ(Thy1.1) CBir1 TCR-Tg reporter mice, whose TCR is specific for an immunodominant microbiota antigen, CBir1 flagellin, under Th1 polarizing conditions. IFN-γ(Thy1.1+) Th1 cells induced colitis in Rag(-/-) mice after adoptive transfer and converted into IL-17(+) Th17, but not Foxp3(+) Treg cells in the inflamed intestines. TGF-β and IL-6, but not IL-1β and IL-23, regulated Th1 conversion into Th17 cells. TGF-β induction of transcriptional factor Runx1 is crucial for the conversion, since silencing Runx1 by siRNA inhibited Th1 conversion into Th17 cells. Furthermore, TGF-β enhanced histone H3K9 acetylation but inhibited H3K9 trimethylation of Runx1- and ROR-γt-binding sites on il-17 or rorc gene in Th1 cells. We conclude that Th1 cells convert into Th17 cells under inflammatory conditions in intestines, which is possibly mediated by TGF-β induction of Runx1.

The 3 major types of innate and adaptive cell-mediated effector immunity

The immune system has tailored its effector functions to optimally respond to distinct species of microbes. Based on emerging knowledge on the different effector T-cell and innate lymphoid cell (ILC) lineages, it is clear that the innate and adaptive immune systems converge into 3 major kinds of cell-mediated effector immunity, which we propose to categorize as type 1, type 2, and type 3. Type 1 immunity consists of T-bet(+) IFN-γ-producing group 1 ILCs (ILC1 and natural killer cells), CD8(+) cytotoxic T cells (TC1), and CD4(+) TH1 cells, which protect against intracellular microbes through activation of mononuclear phagocytes. Type 2 immunity consists of GATA-3(+) ILC2s, TC2 cells, and TH2 cells producing IL-4, IL-5, and IL-13, which induce mast cell, basophil, and eosinophil activation, as well as IgE antibody production, thus protecting against helminthes and venoms. Type 3 immunity is mediated by retinoic acid-related orphan receptor γt(+) ILC3s, TC17 cells, and TH17 cells producing IL-17, IL-22, or both, which activate mononuclear phagocytes but also recruit neutrophils and induce epithelial antimicrobial responses, thus protecting against extracellular bacteria and fungi. On the other hand, type 1 and 3 immunity mediate autoimmune diseases, whereas type 2 responses can cause allergic diseases.

Human Th1 dichotomy: origin, phenotype and biologic activities

The great variety of pathogens present in the environment has obliged the immune system to evolve different mechanisms for tailored and maximally protective responses. Initially, two major types of CD4+ T helper (Th) effector cells were identified, and named as type 1 (Th1) and type (Th2) cells because of the different cytokines they produce. More recently, a third type of CD4+ Th effectors has been identified and named as Th17 cells. Th17 cells, however, have been found to exhibit high plasticity because they rapidly shift into the Th1 phenotype in the inflammatory sites. Therefore, in these sites usually there is a dichotomic mixture of classic and non classic (Th17-derived) Th1 cells. In humans, non classic Th1 cells express CD161, as well as the retinoic acid orphan receptor C, IL-17 receptor E, IL-1RI, CCR6, and IL-4-induced gene 1 and Tob-1, which are all virtually absent from classic Th1 cells. The possibility to distinguish these two cell subsets may allow the opportunity to better establish their respective pathogenic role in different chronic inflammatory disorders. In this review, we discuss the different origin, the distinctive phenotypic features and the major biologic activities of classic and non classic Th1 cells. This article is protected by copyright. All rights reserved.

Th17 and non-classic Th1 cells in chronic inflammatory disorders: two sides of the same coin

Th17 lymphocytes, beyond their protective role in the clearance of extracellular pathogens, also play a role in the pathogenesis of several autoimmune and inflammatory diseases, such as multiple sclerosis, rheumatoid arthritis, inflammatory bowel diseases, psoriasis and contact dermatitis. Nevertheless, they are very rare at inflammatory sites in comparison with other T cell subsets. Recently, this rarity has been explained by the finding that Th17 cells rapidly shift into the Th1 phenotype in the presence of IL-12 and/or TNF-α as well as by the fact that they possess self-regulatory mechanisms limiting their own expansion. Th17 lymphocytes that have shifted towards a Th1 phenotype seem to be particularly aggressive and more pathogenic than the Th17 unshifted cells. As a consequence, the Th17-derived Th1 cells, named non-classic Th1 cells, can become a possible target for the therapy of some inflammatory disorders. In particular, convincing evidence has recently been accumulated indicating that this subset can play a role in Crohn's disease and juvenile idiopathic arthritis. More importantly, it has been shown that TNF-α inhibitors, which are used for the treatment of such diseases, appear to be able to inhibit the transition of Th17 lymphocytes to the non-classic Th1 phenotype, and thus they possibly help to dampen inflammation and arrest disease progression. Based on this context, the definition of the soluble factors involved in the shifting from Th17 towards non-classic Th1 subset as well as the comprehension of their respective pathogenic role in human inflammatory disorders would be of great help for developing novel therapeutic strategies.

Th17 plasticity: pathophysiology and treatment of chronic inflammatory disorders

CD4+ T cells can be classified from a functional point of view in different lineages, the most extensively studied being the Th1, Th2, and Th17. Recent evidence suggest that the acquisition of a certain phenotype is not irreversible, and lymphocytes can acquire features of different effector fates upon adequate stimuli. In particular, Th17 lymphocytes in inflammatory conditions can start to produce IFN-γ or IL-4, shifting towards a Th17/Th1 or Th17/Th2 phenotype, respectively. Th17/Th1 and Th17/Th2 cells, seems to be more pathogenic than the unshifted cells. The possibility to interfere with this modulation of phenotype can be considered a possible target for developing novel therapeutic strategies in those inflammatory conditions in which the shifting of Th17 cells, particularly towards the Th1 phenotype, can occur.